OK then I need to get a proper Flashlight for candling. Because the one I had was a penlight. I thought the picture odd too but then I had to find a picture of excatly what I was seeing. I am not seeing any air cells at all in any of the eggs. I am sure its my inexperience. I have a flashlight about as big as yours but didnt have it with me its one of those ones that has LED lights and they are so bright they will blind you if you look at it straight on.
By the way I am seeing veins on your first two eggs. I will get this down. Its a good thing I am doing this now to learn how with my own eggs rather than ones I buy.
You should be able to see the air cells very clearly by now, (especially in your chicken eggs, which develop a little faster and have thinner shells). Focusing on the air cells is basically how I determine fertility early in all my eggs, the shade of the air cell is really pale/light compared to the shade of the egg contents and pretty noticeable (to me anyway) after about just 4 days of incubation.
Kind of odd that egg in the pic you posted has the dark area up at the big end of the egg, and no visible air cell... might just be due to how the pic was taken and the egg was held, or even how it was set in the incubator. I incubate all my eggs in egg turners, pointy end down and the dark area always settles to the bottom/pointy end
For whatever reason, (compounded by my overwhelming lack of photography skills)... I can't EVER get veins/embryo growth to show up well in my candling pics... frustrating as ****. You can at least see that the air cells are very visible at the top of my eggs tho. I'm running the RH a little low in 'bator with the yellow egg turners (maintaining in the high 30% range), higher in the 'bator with the blue egg turner (maintaining in the low 50% range)... Notice the air cell size difference, it's a lot more than I expected it to be, kinda has me worried now, lol
Day 8 for these eggs:
Day 1 for this egg, for comparison. Air cell is hard to see: